Abstract--Space-time adaptive processing (ST AP) algorithms with coprime arrays can provide good clutter suppression po - tential with low cost in airborne radar systems as compared with their uniform linear arrays counterparts. However, th e performance of these algorithms is limited by the training samples support in practical applications. T o address this issue, a robust two-stage reduced-dimension (RD) sparsity-aware S T AP algorithm is proposed in this work. In the first stage, an RD virtual snapshot is constructed using all spatial channels but only m adjacent Doppler channels around the target Doppler frequency to reduce the slow-time dimension of the signal. In the second stage, an RD sparse measurement modeling is formulated based on the constructed RD virtual snapshot, wh ere the sparsity of clutter and the prior knowledge of the clutte r ridge are exploited to formulate an RD overcomplete diction ary. Moreover, an orthogonal matching pursuit (OMP)-like metho d is proposed to recover the clutter subspace. In order to set the stopping parameter of the OMP-like method, a robust clutter rank estimation approach is developed. Compared wi th recently developed sparsity-aware ST AP algorithms, the si ze of the proposed sparse representation dictionary is much smal ler, resulting in low complexity. Simulation results show that t he proposed algorithm is robust to prior knowledge errors and can provide good clutter suppression performance in low sam ple support. Index T erms--Robust space-time adaptive processing, coprime arrays, prior knowledge, reduced-dimension, sparsity-aw are.

Affinity propagation clustering (AP) has two limitations: it is hard to know what value of parameter 'preference' can yield an optimal clustering solution, and oscillations cannot be eliminated automatically if occur. The adaptive AP method is proposed to overcome these limitations, including adaptive scanning of preferences to search space of the number of clusters for finding the optimal clustering solution, adaptive adjustment of damping factors to eliminate oscillations, and adaptive escaping from oscillations when the damping adjustment technique fails. Experimental results on simulated and real data sets show that the adaptive AP is effective and can outperform AP in quality of clustering results.